Technology Developments and Researches
for Co-existence of Geothermal Power
Plant and Hot Spring Spa Businesses

Kasumi Yasukawa
Renewable Energy
Research Center, AIST1

Contents• Introduction• Overall System Design• Geochemical Investigation on Relationshipbetween Geothermal Reservoir and Hot
Spring Aquifer• Development of Hot Spring Monitoring
Device• Summary2Introduction• Japan has geothermal potential of 23 GWe (Muraoka, 2009) but thecurrent installed capacity in the nation is merely 520 MWe.
• The three major barriers include: 1) regulations on natural parks, 2)development risk and cost and 3) social acceptance.
• The former two barriers were largely mitigated by supportive policy ofthe central government after the nuclear accident in March 2011.
• Social acceptance still remains a major problem, especially due toopposition by groups of hot spring owners fearing degradation of hotsprings.
• Therefore to gauge acceptability of this impact on local residents andstakeholders, research related to social acceptance of geothermal
development has been conducted in AIST.
Muraoka, 2009. Resource Assessment, Geothermal power generation,
Thermal and Nuclear Power Engineering Society, 61-69, (in Japanese).
3

Contents• Introduction• Overall System Design• Geochemical Investigation on Relationshipbetween Geothermal Reservoir and Hot
Spring Aquifer• Development of Hot Spring Monitoring
Device• Summary
4Overall System Design (OSD)• Regional communities are
based on stable mutual
relationships throughhuman activities such as
agriculture, industry,construction, transportation,service industries, etc.
• It is expressed by “regionaleconomic circulation model”(Soma, 2015).
• A balanced circulation ofmoney, persons and goods,etc., exists to some extent
in regions.

Conceptual diagram of regional economic circulation
model before geothermal development (Soma et al,2015)
5

The “regional economiccirculation model” changes
after geothermal development.
Such development may makesome stakeholders happy andothers unhappy thus triggering
opposition campaigns.
For better social acceptance,transparency of information
among all stakeholders isessential. Idealistically forequity, “system design” shouldbe agreed by all stakeholders.
So, a concept of OSD isdeveloped.

Conceptual diagram of regional economic circulation model
after geothermal development (Soma et al, 2015).

Soma et al., 2015. Conceptual Study of Overall System Design of Geothermal Energy Systems forAchieving Universal Use in Japanese Social Condition, Proc. WGC2015, Melbourne, Australia.

OSD optimization at a time step•••

In OSD, several possibleenergy utilization
systems (= methods),
such as simple flush
system or binary withheat supply system will
be suggested.
Detailed design of eachmethod will be adjusted
to optimize objective
parameters, such as
business profitability andsocial acceptance.
The best method withhighest objective
parameters at the timestep may be chosen.

7OSD transition
with time•

The best method may varywith time, because;ü exploration result gives moreaccurate data on subsurface
system, which are input data
for OSD, andü more communication may
improve social acceptancethat enlarges the range ofacceptable methods.

•Thus best method maychange several times andreaches the final OSD when
final decision should be done.

8Trade-offs in OSD
••
•

•
•

•

•

•

The OSD is based on an idea of“Multi-objective optimization”.
In many case trade-off exist.
Optimal solutions on the maximum
limitation line of two trade-off
valuations are shown in the Figure.
Possible design solutions areplotted within the gray zone.
“A” and “B” are “Pareto optimalsolutions” while “C” is merely oneof feasible solutions.
Pareto optimal solution can be
defined for three or more trade-off
elements in a multi-dimensional
space.
OSD only show these trade-offs:
Pareto solutions (Miettinen, 1999) plotted for axes
decision on choice of solution isof trade-off factors, profitability of private company
done by stakeholders.
and regional social acceptance
Therefore, visualization of benefit
and risk is an important roll of OSD.
Such tools may be developed inMiettinen, K., 1999. Nonlinear Multiobjective Optimization.
the future.
Kluwer Academic Publishers, Boston, ISBN 0-7923-8278-1
9

Contents• Introduction• Overall System Design• Geochemical Investigation on
Relationship between Geothermal
Reservoir and Hot Spring Aquifer• Development of Hot Spring MonitoringDevice• Summary
10

Characteristics of 5 Types
Hydraulic relationship of hot springs withgeothermal reservoir

aquiferSO42-geothermal
reservoir

Identical
thermal water

Seepagethermal wateraquifergeothermal
reservoirSteam heatedHeat
conduction

Independent

11

Possible influence of geothermal fluid
production onto hot spring aquifer

Type 1
Identical
thermalwater

Type 2
Seepagethermalwater

Type 3
SteamheatedType 4Heat
conduction

Type 5
Independent

Large

MediumSmall

Very small

None

Possible major
influence

Flow rate

Flow rate,
Dilution

Chemicalcomponent--

Possible small & longterm influence

Temperature

Temperature

Temperature

Temperature

Possible minor
Chemicalinfluence under specific component*
condition

Chemicalcomponent*

Flow rate**

Temperature*

Relationship togeothermal reservoir
Possibility ofgeothermal
development influence

12

Improvements of the type analysis• Two types are newly added for a better type analysis.

watersupply
CO2

geothermal
well
(b)

(a)
aquiferCO2watersupply

CO2

aquifer
HCl, SO2, H2S

CO2volcanicgas

other CO2
sources
geothermal
reservoir
CO2water supply

volcanic gas
HCl, SO2, H2S, CO2

magma(a) CO2 supply type and (b) volcanic gas supply type13

Schematics of 7 Typesrainwaterrecharge

waterrecharge

GPP Type 1

geothermal well

Volcanic
gas supply
heatCO2supply

other CO2sourcesType 4Heat conduction
Identical thermal waterType 3
Steam heatedType 2
Seepage thermal water

hot spring wellType 5
Independenthydrothermal systems

CO2 supply
CO2magmachamber

CO2
volcanic gas

14

Flow chart of type analysis
Simple type analysis by hot spring chemistry
Steam onlyor natural
fumarole

Hot spring
temperatureanion type

90℃≦TCl- type (≦80%)

yes noTDS(mg/L)

Cl- type (80%≦)

Type 2: Seepage
thermal waterSO4- typepH<3 andCl->SO4-

Type 1: Identical
thermal waterothers
60℃≦TT＜90℃

yes noAll anion data
(Cl-, SO4-,HCO3-) exist?

noVolcanicgas supply
No judgment(poor data)

CO2 supply

Cl- type
Type 3:
Steam heated

SO4- typeyesothers
25℃≦T
T＜60℃

T＜25℃

SO4- type≧1000

HCO3- type<1000

others<1000

HCO3- type≧1000

othersNo T data

Type 4: Heatconduction

Type 5:
Independent

TDS: Total dissolved solids
15

Ternary Diagram of hot springs in Kuju area
Deriving from flowchart:“Identical” and “Seepage” arerich in Cl-.
”Steam heated” is rich in SO42.
“CO2 supply” is rich in HCO3-.
“Heatconduction”and“Independent” types distributein wide range of this diagram
because they have various
kinds of chemistry.
Characteristic of this region:“Heat conduction” has lower SO42- content
than “Independent”.
High temperature hot springs (>90℃) are“Identical” except for 2 cases of “Seepage”.
“Identical” has clearly higher Cl- content
than “Seepage”, showing that the threshold
is appropriate. （Cl- content > 80% of allanion）

16

Temperature-TDS plot of hot springs in Kuju
Total dissolved solids: TDS (mg/L)

7,000
6,000
5,000
4,000
3,000
2,000
1,0000010203040506070
Temperature (℃)

8090100

Characteristic of this region:“Independent” has lower temperature and TDS than “Heat conduction,” which is not always the caseaccording to the flow chart.
17Geographicalplot of hotsprings in Kuju
Two commercial GPP and a hotel GPP exist.
No “Identical thermal water” exists in this area.
GPPs are located in regions where “Seepage”
and “Steam heated” densely exist, suggestingthat this kind of hot spring type specification may
be applied for geothermal exploration.
Most of the hot springs which might beconnected to a geothermal reservoir exist within
1km from GPPs.
The hot springs near Otake GPP and Hatchobaru
GPP may be connected to both or either of them.
Monitoring is needed to identify their connection.
“Steam heated” densely exist around KK Hotel
GPP. Yoshibu area may have a geothermal
reservoir, but it is not clear if it is connected to thereservoir of KK Hotel GPP.
“CO2 supply” in the northern area must not be
connected to a geothermal reservoir. Except forthese ten “CO2 supply” in the north, 36 hotsprings out of 49 (70%) in this map are locatedwithin 1km from GPP.

18Contents• Introduction• Overall System Design• Geochemical Investigation on Relationshipbetween Geothermal Reservoir and Hot
Spring Aquifer• Development of Hot Spring Monitoring
Device• Summary19

Coexistence of geothermal power generation with hot springs

One of the key issues forconsensus from local
community to geothermal
power generation

Lack of scientific data toquantitatively evaluate effects
of geothermal development tohot springs
Data with nature of- continuous- reliable- high resolution

NEDO Project
Concept of the monitoring system of hot springs
Multifunctional monitoringby sensors (Temp.,
Flowrate, Conductivity)and plug–in sensors

Air temp.
sensorPlug-insensors(water leveletc.)

Wired/wireless datatransmission capability

Flexible interface tovarious types of pipes

Flexible powerinterface (AC/DC)
Removaldata
storagePV (optional)
Battery forstabilization

NEDO ProjectSpecifications of the monitoring system of hot springs
Dimension：

300 mm(W)×200 mm(H)×200 mm(D)Weight：<4 kg（25A pipe interface）

Flow：

Range 10〜100 L/min, Resolution 0.1 L/min.

Temperature：Range 0〜100 ℃，Resolution 0.1 ℃

Electric conductivity： Resolution 0.01 mS/cm
Plug-in sensor：

water level，Cl，temperature，pressure etc.

Sampling rate：

1 sample/min.

Data transmission：

TCP/IP, 3G, LTE, ISDN

Pipe interface：

Connect-able to major pipes used in hot springs

Price:

2k USD in mass production phase

NEDO ProjectPrototype and field experiment

NEDO Project
Field experiments

Hot spring temperature

Precipitati
onDate, September 2015
Atmospherictemperature
Precipitation

Temperature(oC)

Temperature(oC)

NEDO Project
Data analysis

Date, September 2015

The daily averages of hot spring temperature derived from theobservations of: every second (dotted line), every hour (green line),
everyday noon (pink line) and every midnight (blue line). Every hour isenough sampling frequency. Saishu et al. (2016) Jour. Geotherm. Res. Soc.
Japan Vol. 38. No. 4, P.115-126.

Contents• Introduction• Overall System Design• Geochemical Investigation on Relationshipbetween Geothermal Reservoir and Hot
Spring Aquifer• Development of Hot Spring MonitoringDevice• Summary26

Summary• To gauge acceptability of this impact on local residents
and stakeholders, research related to social acceptance ofgeothermal development has been conducted by AIST.
• Overall System Design (ODS) is a system design concept
to maximize both business profitability and socialacceptance. More study is needed for its realization.
• Geochemical analysis of hot spring fluid may help
planning of hot spring monitoring to avoid interference ofgeothermal reservoir operation. It may also be used forgeothermal exploration.
• Hot spring monitoring device has been developed andapplied for several domestic hot springs.
27